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May 10, 2023

Evaporative Coolers and Legionella: What You Need to Do

Legionella pneumophila bacterium, the causative agent of Legionnaires disease, 3D illustration

Legionella is a type of bacteria found in water systems that can cause Legionnaires’ disease when breathed in. Evaporative coolers can create an ideal environment for dangerous levels of Legionella growth and spread, due to stagnant water and warm, humid conditions. 

To control Legionella in evaporative coolers, regular cleaning, monitoring and testing, water management programs, staff training, and Legionella water filters should be implemented. Doing all of this in compliance with legislation and guidelines is vitally important.

This guide provides all the information you need to prevent and control Legionella bacteria in evaporative coolers and hot and cold water systems as a whole, and explains your legal responsibilities. 

What Counts as an Evaporative Cooler?

Evaporative coolers are a type of air conditioning unit that works by evaporating water into the air to cool it down. They are also known as swamp coolers, desert coolers, or air washers. 

These systems use a fan to draw warm air over a wetted pad or filter, which causes the water to evaporate and the air to cool. This cooled air is then circulated back into the building or room, reducing the temperature and increasing humidity.

Evaporative coolers can come in various sizes and types, from small portable units designed for personal use, to large commercial systems that can cool entire buildings. They are commonly used in areas with hot, dry climates, where traditional air conditioning systems can be less effective or less energy-efficient. 

Evaporative coolers may be found in:

  • Homes
  • Offices, small or large-scale commercial
  • Factories
  • Warehouses
  • Outdoor events

Why Does Legionella Thrive in Evaporative Coolers?

Legionella bacteria thrive in evaporative coolers due to the warm, humid conditions they typically provide. Evaporative coolers draw in hot, dry air and pass it through a wet medium, such as a cooling pad or a series of nozzles, to lower the air temperature. In the process, the water used for cooling becomes stagnant. It can then more easily become contaminated with organic matter, such as algae, bacteria, and other microorganisms, which provide a food source for Legionella bacteria.

How Legionella bacteria grows and spreads

The Dangers of Legionella in Evaporative Coolers

The presence of Legionella bacteria in evaporative coolers can pose a significant risk to human health. When people inhale droplets of contaminated water containing Legionella bacteria, spread by recirculated air as in evaporative coolers they can develop Legionnaires’ disease. This is a severe form of pneumonia that can result in death in vulnerable groups.

It is therefore vital to take appropriate measures to prevent and control the growth and spread of Legionella bacteria in evaporative coolers, such as regular cleaning and disinfection, water management programs, and Legionella risk assessments.

Legalities Surrounding Evaporative Coolers and Legionella Control

The Health and Safety at Work etc. Act 1974 is the primary legislation governing the control of Legionella bacteria in the UK, placing a duty of care on employers and facilities manager to ensure the health and safety of employees and occupants who may be affected. The Control of Substances Hazardous to Health (COSHH) Regulations 2002 provides a framework for controlling Legionella bacteria in the workplace and elsewhere.

For practical guidance on the implementation of Legionella control measures in water systems, HSE’s Approved Code of Practice (ACOP) L8 and HSG274 Legionnaires disease: Technical guidance provide useful information. They set out the requirements for Legionella risk assessments, management plans, and the monitoring and testing of water systems. Failure to comply with these legal requirements can result in serious consequences, including fines, legal action, damage to business reputation, and even forced closure.

What You Need to Do

It is crucial for employers and duty holders to keep up to date with changes to legislation and guidance, as non-compliance with legal requirements surrounding Legionella control can have significant consequences. Ensuring compliance with legal requirements can also help to safeguard the health and safety of employees and other stakeholders, as well as protect the reputation and financial well-being of the business.